[PATCH] Make c-exp.y work with Bison 3.8+

[Simon Marchi]

> According to:
>
> 	https://www.gnu.org/software/bison/manual/html_node/The-YYPRINT-Macro.html
>
> ... the YYPRINT macro has been replaced with %printer a while ago.  So
> it sounds like by just disabling the use of YYPRINT, we are losing some
> debugability.  It would be nice to move to the "new" system, and just
> not use YYPRINT anymore.  Non-Bison yaccs don't generally support
> %printer (ref: John Baldwin on IRC), so we might still have to keep both
> %systems.  Or just require Bison.
>
> But the patch looks good, in the sense that it unbreaks the build, and
> it's definitely better to have a program that builds with a bit less
> debug output than a program that doesn't build, so I think it can be
> merged as-is.
>
> Simon
>

I pushed this on Christian's behalf.

Simon